In general, a blood circuit included in a dialysis apparatus or the like basically includes a flexible tube that allows a fluid, such as the blood of a patient, a physiological saline solution, or a drug to be given, used in a medical site to flow therethrough and connects various elements such as a dialyzer and an air-trap chamber to one another. A hitherto known clamping device for arbitrarily intercepting a desired position of such a flexible tube includes a one end portion having a first projection on the inner side thereof and a locked part at the tip thereof, an other end portion having a second projection at a position thereof facing the first projection and also having a locking part capable of locking the locked part, a middle portion continuous with the one end portion and with the other end portion, and an insertion hole allowing a flexible tube to be inserted between the first projection and the second projection (see PTL 1, for example).
When the one end portion is pressed and is brought closer to the other end portion, the locking part locks the locked part, whereby a clamped state is established. Furthermore, when the other end portion is bent, the locked part locked by the locking part can be unlocked, whereby an unclamped state is established. In the clamped state, the first projection and the second projection are positioned close to each other and thus clamp the flexible tube. Accordingly, the flow of the fluid (blood, a physiological saline solution, or the like) can be intercepted arbitrarily at the clamped position.